suprachiasmatic nucleus

(noun)

cluster of cells that is considered to be the body's internal clock, which controls our circadian (day-long) cycle

Related Terms

Examples of suprachiasmatic nucleus in the following topics:

  • Visual Processing

    • Finally, there is the pathway from the retina to the suprachiasmatic nucleus (SCN) of the hypothalamus.

  • Circadian Rhythms

    • The body's master clock, or the suprachiasmatic nucleus (SCN), controls the production of melatonin, a hormone that makes you sleepy.

  • Seasonal Affective Disorder and Jet Lag

    • Another theory is that the cause may be related to melatonin which is produced in dim light and darkness by the pineal gland , since there are direct connections, via the retinohypothalamic tract and the suprachiasmatic nucleus, between the retina and the pineal gland.

  • Sensory Modalities

    • Receptor cells disseminate onto different neurons and convey the message of a particular taste in a single medullar nucleus.
    • One particular component, the suprachiasmatic nucleus , is responsible for the circadian (daily) rhythm, while other cell clusters appear capable of shorter-range (ultradian) timekeeping.

  • The Nucleus and Ribosomes

    • Found within eukaryotic cells, the nucleus contains the genetic material that determines the entire structure and function of that cell.
    • One of the main differences between prokaryotic and eukaryotic cells is the nucleus.
    • The nucleus stores chromatin (DNA plus proteins) in a gel-like substance called the nucleoplasm .
    • Lastly, the boundary of the nucleus is called the nuclear envelope.
    • The nucleus is the control center of the cell.

  • Nuclear Binding Energy and Mass Defect

    • A nucleus weighs less than its sum of nucleons, a quantity known as the mass defect, caused by release of energy when the nucleus formed.
    • This mass, known as the mass defect, is missing in the resulting nucleus and represents the energy released when the nucleus is formed.
    • As the size of the nucleus increases, the strong nuclear force is only felt between nucleons that are close together, while the coulombic repulsion continues to be felt throughout the nucleus; this leads to instability and hence the radioactivity and fissile nature of the heavier elements.
    • This graph shows the nuclear binding energy (in MeV) per nucleon as a function of the number of nucleons in the nucleus.
    • Notice that iron-56 has the most binding energy per nucleon, making it the most stable nucleus.

  • Photon Interactions and Pair Production

    • Pair production refers to the creation of an elementary particle and its antiparticle, usually when a photon interacts with a nucleus.
    • Below is an illustration of pair production, which refers to the creation of an elementary particle and its antiparticle, usually when a photon interacts with a nucleus.
    • In nuclear physics, this reaction occurs when a high-energy photon (gamma rays) interacts with a nucleus.
    • The nucleus in the process carries away (or provides) access momentum.
    • Describe process of pair production as the result of photon interaction with nucleus

  • Characteristics of Eukaryotic Cells

    • Because a eukaryotic cell's nucleus is surrounded by a membrane, it is often said to have a "true nucleus. " Organelles (meaning "little organ") have specialized cellular roles, just as the organs of your body have specialized roles.
    • Typically, the nucleus is the most prominent organelle in a cell.
    • Eukaryotic cells have a true nucleus, which means the cell's DNA is surrounded by a membrane.
    • The nuclear envelope is a double-membrane structure that constitutes the outermost portion of the nucleus.
    • The nucleoplasm is the semi-solid fluid inside the nucleus where we find the chromatin and the nucleolus.

  • Clusters of Neuronal Cell Bodies

    • A nucleus can either by a relatively compact collection of neurons or a distinctly identifiable group of neurons spread over a large area.
    • In neuroanatomy, a nucleus is a brain structure consisting of a relatively compact cluster of neurons.
    • In anatomical sections, a nucleus shows up as a region of gray matter, often bordered by white matter.
    • In addition, nucleus can refer to an identifiable distinct group of neurons that can spread over an extended area.
    • For example, the reticular nucleus of the thalamus is a thin layer of inhibitory neurons that surround the thalamus.

  • Multielectron Atoms

    • In hydrogen-like atoms (those with only one electron), the net force on the electron is just as large as the electric attraction from the nucleus.
    • However, when more electrons are involved, each electron (in the $n$-shell) feels not only the electromagnetic attraction from the positive nucleus, but also repulsion forces from other electrons in shells from '1' to '$n$'.
    • Therefore, these electrons are not as strongly bonded to the nucleus as electrons closer to the nucleus.
    • As an approximation, the effective nuclear charge on each electron can be estimated by: Zeff=Z−σZ_\text{eff} = Z - \sigma, where $Z$ is the number of protons in the nucleus and σ\sigma is the average number of electrons between the nucleus and the electron in question. σ\sigma can be found by using quantum chemistry and the Schrodinger equation or by using Slater's empirical formula.
    • A multielectron atom with inner electrons shielding outside electrons from the positively charged nucleus